alright..i have looked everywhere, including the owners manual lol..and i cant figure this out.

Just below and to the left of the steering column is a little buttion that if pulled out, is on..and pushed in is off..and on it it says "RR HEAT WATER"

this is an enigma. Does anyone have any idea what the hell that is?
Its a 1972 hearse..472 engine.

hmm...maybe it controls the rear heater? Does it have one of those?